Cloud-based Private Querying of Databases by Means of Homomorphic Encryption

This paper deals with several use-cases for privately querying corpora of documents in both settings where the corpus is public or private with respect to an honest-but-curious infrastructure executing the query. We address these scenarios using Fully Homomorphic Encryption (FHE) hybridized with other techniques such as Symmetric Searchable Encryption (SSE) and Private Information Retrieval (PIR) to achieve acceptable system level performances. The paper also presents the prototypes developed to validate the approach and reports on the performances obtained as well as their capacity to scale.